Furnace-roof construction



F. H. LOFTUS FURNACE ROOF CONSTRUCTION Oct. '2, 1928.

5 Sheets-Sheet 1 Filed April 5, 1927 ;w w www w r n H u a .S er m nw Oct. 2, 192&

F. LOFTUS FURNACE ROOF CONSTRUCTION FIB.

INVEINTOR Fred H. LoH'us bg his at'hrneu Oct. Z, 1928. 1586386 F. H. LOFTUS FURNACE ROF CONSTRUCTION Filed April 5, 1927 :5 sheets-sheet' 3 INVENTOR Tred H'. Lol hs by his affo n f Patented Oct. 2, 1928.

PATENT "orrce.

FRED H. LOTU, OF CVPITTSBUEGH, TENNSYLVANIA.

't'UnNAcE-noor* CONSTRUCTON.

v Apiiication filed. April 5, 1927. Serial No. 181,062.

This invention-relatesto furnace root construction, and more especially to a 'roof contruction :tor use in basic'open hearth furnaces. V v

Inprior open hear-th i urnace construction theroof and wails 'usually meet ata point of about 5 feet above the 'fore piate level. The 'root hasa uniform curvature, and usually rises .about 2 feet for an 18 foot spam. The root is constructed entirely of silica brick and is'supported on skewbacks, which are located immediately [above the walls and rest on a channel Construction supported by the binding members of the' furnace known as' 'buck-stays. i

'In this particular type of 'construction there is a. segment of the root, adjacent the skew-backs along the front and back Wa lis and over the hearthofthe furnace, which is sub3e`ct to-rapid destruction dueto the opera- The destructionis aused by abrasion and chemical 'reaction` During the init-ia'l stage of the heat, When the urnace is 'charged with lime and scrap, the scrap fills the laboratory of the furnace almost ;to the jroof, leaving a channel between :the 'sera-p and 'the back 'wall and also a channel between the sc'rap and the front wall. Thejscrap causes the fianie to dividegso that a 'portion of't passes along the back wall and the remain'- der along the `front wall. Due 'to the fact that the skew-backs are the lowest points on the root, the flame comes in contact with the brick w'rk'thus causing asectionof the root about& feet inwidth to become highly heated. The gases, 'during this initial stage of the heat; abrade the 'brick work of the roof in these regions 'until the scrap charge becomes melted. After the 'iron has been charged, and the lin e *begins to rise, the gases become laden with basic oXides. During this operation, the furnace has been constantly gaining in temperature, and the segments 'along the skew' backs are much higher in temperature than the remaining portion of the roo f. Duejto the high temperature of the 'segmente the basic oXides 'react with the acid 'material causing a sweating or fiuxing action With the prior roof constructions it is 'Very diflicult 'to make repairs' in the roof. When` making repairs it is necessary to chill .the `furnace which' has a deleterous effect on the 'brick-work 'and sha'pe of the root It is usually* necessary to 'make initial repairs between '75 and 100 heats, and thereafter about 'every to 7 5 heats. This is accomplishedby replacing a 'small 'section of the roof at a time, andby suspending the centers 'wth'wire Secured to'the structural' construction 'over the roof. After about three such repairs have been made, the 'furnaceman-finds that the cooling and heating of the urnace, 'and uneven expansion 'of the old -and new brick wir-ork,` weakens the roo f to* such 'an ex'tent that 'it is necessary to replacethe entire root; although the material remaining in the central portion of the 'roof may still be from Seven to nine inches :in thickness. u v r y i -In prior roof Construction'no provision is made for Variations in expansion between 'the interor and eXteror surface of the roof. The'presentnethod is to increase the span'of the root, upon heating, by Ineans o'f the tie rods,'the th'rustof the roof causingthe bindi ing members ofthe'turnace to move outwardly. This'increaseinspan will provide added space for the interio'r surface, butowing to the lesser expansion of the exteror surface of theroof, gaps willbe fornied in the brick work. Buch 'a condition requires the 'interior surface, which is' at the maximum "temperaturs, to support` the entire load'of the roof.

This effectis unsatisfactory due to the weakened co'nd'ition of the material at such time. The condition 'results in spalling and cracking' of the 'brick work, and, when the root becomes thin, causes saggng due to the gaps between the brcks 'their outer extreinity.

With my invention I haveprovided a construction injwhich the main section of the roof' outside the usual zo ne of destruction is supported independent'ly of the segments which are `rapidiy destroyed; i In`p1ace of sihca'I have substitutedchromematerial or other suitable 'non-reactive material in the zone of destination, to counter-act the chemical reaction which exists therein; I 'am able to'substitute this 'material 'by carrying the load and thrust of the main root on auxiliary members," so that the relatvely short spans in the zones of destruction are relieved of the load and thrust ofthe roofas awhole.

By actual` testchrome composition material to the fullest extent the materialin the center of the roof.

In the accompanying drawngs Figure 1 is a vertical transverse section through an open hearth furnace embodying the improved roof Construction of the present invention; Figur-e 2 is a fragmentary longitudinal sectional View of the furnace, on a smaller scale than Figure 1, taken along the line of the thrust members of the present Construction; F igure 3 is an enlarged detail view, partly in elevation and partly in section, showing Vone of the thrust members of the root and the elements immediately associated therewith; Figure 4 is anisometric view of the containing members of the thrust member assembly; Figure 5 is a cross sectional view onthe line 5-5 of Figure 4; Figure 6 is an isometric View of a number of the refractory members to be inserted in thecontaining members to complete the assembly; and Figure7` is a cross sectional view on the line .7-7 of Figure 4, but showingthe refractory members in position. i

In the drawings the reference numeral 1 designates the hearth of the furnace and the reference numeral 2 the buck-stays of the furnace frame; Opposite buok-stays are interconnected by tie rods 3. Extending vertically from' the hearth 1 of the furnace arethe back wall 4 and the front wall 5.

On the walls 4 and 5 are skew-backs 6, which are in contact with the front and back edges of the roof and which are supported by channel members 7.

The roof, designated generally by the reference numeral 8, is formed on a continuous curve, and comprises a central portion 9 formed of silica brick. Adjacent the front and backwalls of the furnace, and supported by the skew-backs 6 are roof segments or portions 10 of a material which is non-reactive to the basic oXides which impinge against these-portions of theroof, in what has been 'herein called the 'Zones of destruction. Such material is desirably chrome brick, but may be' of magnesite brick or other suitable refractory material 'which is non-reactive under the conditionsof operation in the furnace. of chrome or magnesite brick to withstand compressive stresses, and for the purpose of facilitating repairsin. the r'urnace roof, means are provided for supporting' the load and taking the thrustof the central portion eo& the roof independently of these nonreactive portions 10. y

Such means comprise thrustmembers, indicatedgenerally by the reference numeral 11, which are interposed between the central roof portion 9 and the outernon-reactive roofportions 10. The thrust members 11 comprise metallic side members 12 and 13 which "are interconnected by means of brackets 14. When assembled in a furnace Because of the inability material.- As shownin Figures 5 and 6, the

blocks l are so formed as to have an outwardly inclined lower portion' 15 and an inwardly inclined upper portion 15. This conformation of the blocks permits them to be securely held in position by the side members12 and 13, which are angular in section, as shown. In order that the blocks 15 may be inserted between the side members, to be engaged thereby, .the member 13 has a hinged connection 16 with the brackets 14 to which it is attached. This side member may, therefore, be raised to permit the insertion of the refractory blocks, and may be lowered to engage them after their insertion.

The bracket 14, of the assembly is provided with lugs 17 extending upwardly therefrom and having bolt holes for the reception of bolts 18 by which the bracket is connected with the eye 19' of a supporting rod 20. Each of the supporting rods 20 is connected with overhead beams 2liresting on cross beams 22 which are supported by 'the buck-stays 2. The supporting means 'for the rods 20, as shown in Figures 2 and& i

bolt 26 passing through an eye 27 on a comv pression bar 28. 'At the other end of the compression bar is an eye 29 for rec'eiving a bolt' 30 to connect the bar to one of the buck-stays 2. u i i y VVhen in position in the furnace roof the thrust members 11 provide support for ,the roof as a whole, and, because of the thrust bar 28, serve to take the thrust of the cen tral portion 9 of the roof. It should be noted that the flaring sides of the thrust members are in a plane perpendicular to the line of thrust of the roofland it should also be -noted that the metallic side member 12 is :longer than the hinged side member 13. The additional support of the side members prevents shearing of the refractory blocks 15 under the thrust of the central roof portion, 9 and the difl'erence in length of these members is highly desirable. When the roof is new the longer member 12reinforces thejrefracting material against the line' of thrust of the roof. As the roof wears away the line of thrust of the roof moves upwardly, until it, is along such line that the shorter member. 'reinforces the refractory material against it. With this arrangement it is immaterial that the longer member is burned away gradually during the operation of the furnace, as a't such time the shorter member reinforces against 5 the thrust. i a

Becausethe thrust members 11 assume the load and thrust of the greater part or" the root, it is possible toconstruct the portions or segments 10. of the root of the desired non-reactive material even though this material is lacking in compressive strength. Also these portions may be replaced, when necessary without cletriment to the central portion 9 of .the roof.

'The use of the thrust members also provides for the difference in expansion between the interior and exterior surface of the central portion of the root'. When theffurnace is being brought up to temperature, the tie rods 3 may be loosened in the customary m'anner, and the thrust of the root forces the buck-stays 2 outwardly. Due to, the fact thatthe compression bars 28 are rotatably connected with the buck-stays and the thrust members, the thrust members are caused to rotate slightly into the position indicated in dotted lines in Figure 3 of the drawings. This permits a movement of expansion for a greater distance on the interier surface of the central portion of the roof than on its exterior surface. This eflect is possible because the expansion of the chrome brick in the outer roof portions 10 is less than that of the silica brick in the central roof portion 9.

When chrome brick is used as the non-reactive material in the outer roof portions constituting the zones of destruction, it is a possible to secure a much longer life on a 9 inch section of chrome in' this region than would be possible with a 12 inch section of silica brick. It should be understood, however, that in any furnace root constructed of a single material, in which the roof 'wears away more rapidly adjacent a wall or 'walls of the furnace, the use of the thrust members is of great advantage in' facilitating repairs which consist in the replacement of an outer section or sections of the root.

What Iclaim is:

1. In furnace root Construction a root portion of chemically neutral material adjacent a wall of the furnace, and means interposed between said portion and the remainder of the roof arranged to assume the load and thrust of the remainder of the roof.

2. In furnace roof Construction a roof portion of chrome brick acljacent a wall of the furnace, and means interposed between said portion and the remainder of the roof arranged to assume the load and thrust oi" the remainder of the roof.

3. In furnace root Construction roofportions of chemically neutral material acljacent two opposed walls of the furnace, an inter- Vening aportion 'of difl'erent` material, and means interposed between each of the Chemically neutral portion's and the intervening root portion arranged to take the loadand thrust` of the intervening portion.

4. In turnace roofconstruction root por'- tionsof chrome brick adjacent two-opposed walls of the furnace, an intervening portion of different material, and means interposed between each of the chrome brick portions and the intervening portion 'arranged to take the load and thrust of the intervening portion'.

5. In furnace roof Construction compris ing a root formed on 'a continuous curve, twoparallel thrust 'members spacedonopposite sides of the apexfof the roof,` and means' connected with said thrust members and with'the framework of the i urnace for 'assuming the load and thrust of the portion 'of the roof between said thrust members w 6.' In furnace root Construction comprising a roof formed on acont1`nuous curvc,

two parallel thrust members spaced o n op posite sides'of ;the apeX of the roofl supporting members connected with said thrust members and with the framework of 'the `furnace, and compression members connected with said thrust members` and with the framework of the furnace.

7. .In furnace root Construction a root portion of material which is non-reactive to basic laden fumes, and means interposed between said portion and the remainderof the roof arranged to assume the load and thrust ost' the remainder of the roof.

8.` In furnace roof Construction roof portions of a material which is non-reactive to 'basic laden fumes adjacent two opposed members connected with said overhead beam members and with said thrust members, and compression members connected wth sad thrust members and with the framework of a the furnace.

. ber' for interposition between adjaoent roof 'portions comprising spaced metallic side members, a metallio eonneoting member to which said side members are attached, and a filling'of refractory material engaged by said metallie side members. I i

12. In furnace roof Construction a member for interposition between adjacent roof portions comprising spaced metailic side members of unequal length, a metallic connecting member to which said side members are ,attached, and a filling of refrectory materal engaged by said metallio side mem bers.

`13. In furnace roof Construction a member for mterposton between ad acent roof portons comprising spaced metallic 'side members, a metallic oonnecting member to which said side members are attached, one of said side members being pivotally attached to the connecting member, and a filling of refraotory materal engaged by said metallio side members.

14.4 In furnace roof Construction a member for interposition between adjacent roof portions comprising spaced metallio side i members of unequal length, a connecting member to which said side members are attached, one of said side members being pivotally attached to the conneotng member, and

a. filling of refracto'ry material engeged by 3 said side members. y

15. In furnace roof Construction aroof formed on a continuous curve comprising roof portions adjacent two opposed `waJlls of the furnaoe, and intervening-root-portion,

and means interposed between each of the portions adjacent the furnace 'wall' and the intervening portion to assume the load and thrust of the intervening portion.

16. In -furnace roof. Construction a rooi formed on a. continuous curve comprsing a roof portion adjacent one wall of'the' furnaoe, and means interposed between the FRED* H. Lorrns. 

